Optical Sensing Systems For Structural Health Monitoring

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MOS is shortlisted in the category *Product and Innovation Award* in the Ground Engineering Awards 2016 for our works at Crossrail's Farringdon Station

FBG Bridge Monitoring Applications

FBGs can be used to monitor for changes in strain on or within the bridge structure, relative movements between bridge components, tilt of bridge piers and the weight of vehicles using the bridge. MOS has experience applying FBG monitoring solutions to a range of bridges, with some examples of these applications below.

Overweight Vehicle Detection

MOS installed FBGs onto two suspension rods of a Heritage listed bridge in NSW to monitor for vehicles that exceed the bridge load limit. A truck that equalled the bridge's load limit was driven over the bridge several times to understand the weight to strain relationship. This relationship was then incorporated into custom-made software to record strain if the trigger strain was exceeded. Two cameras were then incorporated into the monitoring system and were used to capture images of the overweight vehicles.
For more information on this application, see this case study or contact us.

High Accuracy Relative Movement Monitoring

MOS GFRC Sensor Cables were suspended and held in tension between key bridge components on two bridges to measure relative movements that may occur due to longwall-mine induced subsidence. The sensor cables were installed in a way that allowed relative movements to be represented in an orthogonal co-ordinate system in the horizontal plane with an accuracy of 0.02mm. The data is acquired by a battery powered system at required times and reported to key personnel for further analysis.
For more information, refer to this paper or contact us.

Concrete Bridge Monitoring

MOS installed 8 long-gauge FBG strain sensors on the stepped joints of concrete bridges to monitor for longwall mine-subsidence induced strains. Tensile strains in concrete can result in cracking, making it difficult to monitor using conventional strain sensors. If a strain sensor is located over a crack, the sensor will exaggerate the actual strain within the concrete, while if the sensor is located adjacent a crack, it will report close to zero strain due to the relief in strain that the crack causes.
Monitoring tensile strain on concrete surfaces can be achieved using a long-gauge strain sensor, with any small cracks and relief being averaged out over a long gauge length. For more information on this project, refer to this paper or contact us.

Steel Frame Bridge Monitoring

MOS installed FBG strain sensors onto the each of the four portal frame legs of a bridge with a lift span to verify a strengthening procedure. The lift span was to be strengthened by post tensioning each leg, and the strain sensors were to verify the stress induced. MOS installed four spot-weldable Micron Optics os3155 sensors to the portal frame. These were selected due to their fast and easy installation, which was critical as the installation was completed in one night.
For more information please contact us.
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